Android开发完全讲义（第二版)第四文章之handclock

package net.blogjava.mobile.widget; import java.util.Calendar; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.Rect; import android.os.Handler; import android.util.AttributeSet; import android.view.View; public class HandClock extends View implements Runnable { private int clockImageResourceId; private Bitmap bitmap; private float scale; private float handCenterWidthScale; private float handCenterHeightScale; private int minuteHandSize; private int hourHandSize; private Handler handler = new Handler(); @Override public void run() { // 重新绘制View invalidate(); // 重新设置定时器，在60秒后调用run方法 handler.postDelayed(this, 60 * 1000); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); // 根据图像的实际大小等比例设置View的大小 setMeasuredDimension((int) (bitmap.getWidth() * scale), (int) (bitmap .getHeight() * scale)); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); Paint paint = new Paint(); Rect src = new Rect(); Rect target = new Rect(); src.left = 0; src.top = 0; src.right = bitmap.getWidth(); src.bottom = bitmap.getHeight(); target.left = 0; target.top = 0; target.bottom = (int) (src.bottom * scale); target.right = (int) (src.right * scale); // 画表盘图像 canvas.drawBitmap(bitmap, src, target, paint); // 计算表盘中心点的横纵坐标 float centerX = bitmap.getWidth() * scale * handCenterWidthScale; float centerY = bitmap.getHeight() * scale * handCenterHeightScale; // 表表盘中心点画一个半径为5的实心圆圈 canvas.drawCircle(centerX, centerY, 5, paint); // 设置分针为3个象素粗 paint.setStrokeWidth(3); Calendar calendar = Calendar.getInstance(); int currentMinute = calendar.get(Calendar.MINUTE); int currentHour = calendar.get(Calendar.HOUR); // 计算分针和时间的角度 double minuteRadian = Math .toRadians((360 - ((currentMinute * 6) - 90)) % 360); double hourRadian = Math.toRadians((360 - ((currentHour * 30) - 90)) % 360 - (30 * currentMinute / 60)); // 在表盘上画分针 canvas.drawLine(centerX, centerY, (int) (centerX + minuteHandSize * Math.cos(minuteRadian)), (int) (centerY - minuteHandSize * Math.sin(minuteRadian)), paint); // 设置实针为4个象素粗 paint.setStrokeWidth(4); // 在表盘上画分针 canvas.drawLine(centerX, centerY, (int) (centerX + hourHandSize * Math.cos(hourRadian)), (int) (centerY - hourHandSize * Math.sin(hourRadian)), paint); } public HandClock(Context context, AttributeSet attrs) { super(context, attrs); // 读取相应的属性值 clockImageResourceId = attrs.getAttributeResourceValue(null, "clockImageSrc", 0); if (clockImageResourceId > 0) bitmap = BitmapFactory.decodeResource(getResources(), clockImageResourceId); scale = attrs.getAttributeFloatValue(null, "scale", 1); handCenterWidthScale = attrs.getAttributeFloatValue(null, "handCenterWidthScale", bitmap.getWidth() / 2); handCenterHeightScale = attrs.getAttributeFloatValue(null, "handCenterHeightScale", bitmap.getHeight() / 2); // 在读取分针和时针长度后，将其值按图像的缩放比例进行缩放 minuteHandSize = (int) (attrs.getAttributeIntValue(null, "minuteHandSize", 0) * scale); hourHandSize = (int) (attrs.getAttributeIntValue(null, "hourHandSize", 0) * scale); int currentSecond = Calendar.getInstance().get(Calendar.SECOND); // 将定时器设在0分时执行run方法 handler.postDelayed(this, (60 - currentSecond) * 1000); } @Override protected void onDetachedFromWindow() { super.onDetachedFromWindow(); // 删除回调类 handler.removeCallbacks(this); } }